Knockdown fuel tank



ec, l, 1953 W. s. FLETCHER KNOCKDOWN FUEL TANK wth I ZA/yf/vro/Q: il,MEA/AEL; 5. Effe/ff@ Dec. 1,- 1953 w. s. FLETCHER KNOCKDOWN FUEL TANK 2Sheets-Sheet 2 Filed July 10. 1950 mln,

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@MPM f @i Wm www ,Patented ec. l, 1953 KNOCKDOWN FUEL TANK Wendell S.Fletcher, South Pasadena, Calif., assignor to Fletcher AviationCorporation, Pasa.- dena, Calif., a corporation of `CaliforniaApplication July 10, 1950,' Serial No. 172,960

9 Claims. l

This invention relates generally to containers and more particularly toauxiliary iuel tanks for aircraft adapted for attachment to portions ofthe exterior of the aircraft, for example, the wing tips thereof.

It is common practice te construct auxiliary wing tip fuel tanks twoparts, that is, with an upper and a lower shell, each having aperimetrical bead which is welded to the bead of the other shell. Theparts of the tank are made as stampings and assembled at themanufacturing plant. As will be apparent, such assembled tanks occupyconsiderable space during shipment to aircraft manufacturers and toairelds. In order to obviate this deciency, efforts have been made toprovide tanks which are composed of several components adapted to bereadily assembled at the site where they are to be attached to theaircraft. Such tanks may include two or more coaxial parts which arejoined at their circumferential seams by welding. ln anothermulti-sectional tank, several coaxial sections are joined in end-toendrelationship by axial clamping means, compressible sealing rings beinginterposed between the abutting ends to provide a leak-proof structure.Such a tank is disclosed in my pending application for patent onAuxiliary Tip Fuel Tank, Serial No. 63,822, filed December 6, 1948, andreference is made to this prior application for a detailed descriptionof the means for clamping the several components together. In additionto being collapsible, the tank shown in the application reierred toabove is capable of being shipped in a knockedndown condition with itscomponents in a somewhat nested condition, this being a desirablefeature since all the parts of the tank can be shipped or stored as s,unit in a single package. It has been found, however, that the size ofthe knocked-down structure can be further decreased so as to reducestill further the shipping or storage space required for the tank, whenthe components of the tank are specially designed with this objective inview.

It is therefore an important object of the present invention to providean auxiliary wing tip fuel tank of the multi-sectional type in which theparts are so shaped and dimensioned that they are capable of beingnested together within a very small compass.

Another object is to provide a tank, of the character referred to, inwhich the sections are adapted to be nested to form a shipping package,the length of which is considerably less than one-half the over-alllength of the complete tank. A related object is to provide amulti-sectional tank which, when in knockeddown condition, has a spaceratio of approximately 2:1, that is, two knocked-down tanks can occupyapproximately the same shipping or storage space as one assembled tank.Since such auxiliary fuel tanks are used primarily on mili taryairplanes and are shipped to the airfields for assembly and attachmentto the airplanes, it is apparent that in the event of military conflict,the conserving of shipping space in railway cars, trucks, ships andtransport aircraft is of utmost importance in meeting the supplyrequirements of the Air Force and that the present invention aidsgreatly in bringing about this desirable result.

I have determined that the maximum space ratio, discussed above, is bestattained by making the tank in several sections, one or more of whichhave annular recesses or jogs in their peripheries to adapt thesesections to be nested within other sections of the knocked-down tank,and this is also an important feature and object of the presentinvention. A related object is to provide fairing sections or bandsadapted to be contracted in position surrounding the assem* bled tank inoverlying relation to said annular .recesses so as to maintain thestreamlined contour which is of such vital importance in highspeedmilitary airplanes.

Another object is to provide a knock-down fuel tank in which theadjoining ends of the various sections are sealed against leakage offuel by compressible sealing rings, and in which the sections are soshaped and dimensioned that the sealing rings may be retained in annularsockets of the sections when the latter are in nested relationship so asto facilitate assembly of the tank at the airfield.

Further objects will appear from the following description and from thedrawings, which are intended for the purpose of illustration only, andin which:

Fig. 1 is a longitudinal sectional view through one form of the improvedknock-down auxiliary fuel tank;

Fig. 2 is an enlarged longitudinal sectional view, illustrating themanner in which the various sections and components of the tank shown inFig. 1 can be stacked in nested relation to produce a knocked-downpackage unit suitable for shipping or storing the tank;

Fig. 3 is a view similar to Fig. 1, showingv a knock-down auxiliary fueltank of alternative construction; and

Fig. 4 is a View similar to Fig. 2, showing the components of thealternative tank in nested relationship.

Rererring rst to Figs. l and 2 of the drawings, the knock-down auxiliaryfuel tank 5 is composed of several sheet-metal sections which areassembled in end-to-end relation to produce a tank which is streamlined,the tank being adapted to be detachably connected to the tip of anairplane Wing. The tank 5 includes a forward tip or nose section ofconoidal shape.

having a reinforcing ring I Within its rearward open end and an annularrim 8 surrounding the projecting end of the reinforcing ring, said rim 8having an inwardly directed flange provided with an annular bead 9. Thering 'i and rim B may be suitably joined together and preferably theyare welded to the rearward end of the nose section 6.

The tank 5 also includes an intermediate section l of tubular form. Atits forward' end, the

section l carries a ring Il which has an inwardly directed iiangeprovided with an annular recess l2 in which is disposed a compressiblesealing ring i3. At its rearward end, the section l0 has a reinforcingring lli and an annular rim member having an annular bead I6.

The multi-sectional tank further includes a tail section 2i] which isor" generally frusto-conical shape, The forward portion of the section2U has a reinforcing ring 2l provided with an inwardly directed ilangewhich is formed with an annular recess or socket 22 in which is dis.-posed a compressible sealing ring 23. Substantially midway between itsends, the tail section 2 is provided with an intermediate straightcylindrical portionv 24- of lesser diameter than its forward portion,which intermediate portion forms, in effect, an annular recess or jog 25in the otherwise smooth, frusto-conical contour. Anannular shoulder 26connects the cylindrical recessed portion 2li with the larger diameterforward portion of the tail section 20.

A frusto-conicall fairing element or ring 3Q is disposed in the annularrecess or jog 25 and f is of a contour which fairs into the streamlinedcontour of the tail section 2G. The fairing element 30 is a sheet metalband having clamping strips 3l at its ends, clamping screws 32 beingemployed for drawing the strips toward eachother so as to clamp thefairing element in place.

At its rearward or aft end, the tail section 20 has a bowl-shapedelement 33 provided-with a tapered circular side vvallv 34, thiswallfbeing welded to the interior ofthe rearwardend ofv the tail sectionand projecting therefrom to provide an annular flange-like seat portionA plurality of circumferentially spaced nuts 36- are carried by the seatportion 35. The element 33 is also provided with an axial tubularportion nected in end-to-end relationship to provide an auxiliary fueltank 5` off streamlined contour possessing excellent aerodynamic low-lcharact eristics.

To assemble the tank E, the radially extending clamping elements 44 of aclamping means i5 are rst placed within the nose section with theirouter ends engaging the reinforcing ring 'i. The intermediate sectionlil is placed in axial alignment with the nose section i5 with theannular bead 9 entering the annular recess or socket l2 and restingagainst the sealing ring i3. The tail section 2d is next placed againstthe rearward end of the intermediate section l, the annular bead i6entering the annular recess 22 and being disposed against the sealingring 23.

The sections 6, lil and 20 are then secured 'j together in coaxialrelationship by the clamping means l5 which includes a cap 46 disposedin the bearing portion 3l of the element 33 and having a peripheralflange seated against the element. A clamping rod d'1, in the form of along bolt, passes through a central aperture in the cap d6 and has ahead at one end abutting the rearward end of the cap. The other end ofthe rod 4'1 is provided with screw threads to adapt it to be screwedinto a nut element carried by one of the clamping elements 4. Thus, byturning the rod lil, the several tank sections are drawn together andthe sealing rings I3 and` 23 are compressed between the adjoiningsections to provide leak-proof joints. The clamping means 45 is hereinshown in a simpliiied form and reference is made to my applicationreferred to previously, for a more detailed description.

After the tank sections have been assembled in the manner explainedabove, the tail tip 40 is applied to the rearward end of the tailsection 28 and fastened in place by means of the screws lil. The tank 5is then ready for use and may be detachably connected to the tip of anairplane wing by any suitable means, not herein shown. The nose sectionB may be provided with a ller opening @19, and suitable fuel lines (notshown) may be connected to the intermediate section Il).

It is. highly desirable that auxiliary wingv tip fuel tanks be sent tothe airiields in knockeddown condition so that they can be assembled asneeded. Such a procedure results in a consider'- able saving in shippingand storage space. will now be shown, by constructing the tankaccordance with the foregoing description. the various sections canv benested together in close relationship so as to conserve valuableshippingand storage space. By practicing the present invention, the spacerequired for the knoeked-down tank'is reduced to a minimurnso that agreater number oftanks may be contained in a given space.

Assuming that-the various sections 5, 4G, 2nand Si! and tip [iii areindisassembled er knockeddownrelationship, these` tank components arestacked or'nested together asshown in 2- to provide a shippingl unit orpackage ci relatively small proportions. To eieet this desirableresult,the rearward end of the taillseetion Ellis iirstlslid into the openrearward'end of the nosev section 6. Itwill be observed thattherearwardend-of ther tail section- 261v isadapted tobedisposed adjacent theclosedrounded end of the nose section. This desirable-condition is madepossible through theannular recess-nr jogY 251e. the tail sectioniiwhich allows; the flanged cnd Slofthe noseseetion to passover theperiphery of thetail 1 section. At this juncture; the bead 9 -offthenose-section-6fisdisposed1adjacentthetapered-I portion of the tailsection and within the flange element 2l. The fairing band 3i) is nextslid onto the nose section 6 with its end of larger diameter engagingthe periphery of the nose section. The intermediate tank section IS isthen slid over the rounded end of the nose section 6 with its bead iiiresting against the periphery of the frusto-conical fairing band 3Q. Itis to be noted by reference to Fig. 2 that when the tank sections arethus nested together the forward end of the intermediate section, thatis, the end containing the sealing ring I3, aligns with the rounded endof the nose section 6. The conical tail tip iii may be placed within thetail section 2B with its apex disposed within the bearing portion 3lthereof, this operation being carried out either before or following thenesting of the tank sections l0, 2li and 38. After the several tankcomponents have thus been grouped together in nested relationship, theremaining elements, such as the clamping means 5, the cap t6, etc., maybe placed in the tail section 2Q through the open end thereof.

The nested group or package of tank components shown in Fig. 2 isparticularly well adapted for shipping and storage since it occupi-es arelatively small space. By shaping and proportioning the varioussections substantially as illustrated in Fig. 1, and nesting the same asshown in 2, the resulting knocked-down assembly or package occupies aspace which is only a fraction of the space occupied by the assembledtank 5, the space ratio being 1:25. That is to say, approximately 21/2knocked-down groups such as that illustrated in Fig. 2 can be stored inthe space required to store or transport one fully assembled tank 5. Itis thus apparent that a material saving in space required for storingand shipping the auxiliary wing tip fuel tanks is achieved. As will beappreciated, such a conservation of space is extremely important fromthe military standpoint since the utilization of available space inships, railway cars and transport aircraft to greatest advantage is ofutmost importance in order to maintain an adequate supply of militarysupplies to the scene of conflict. In order to provide protection forthe nested tank components, the latter may be enclosed in a suitablecrate, carton or other rectangular container. Upon arrival of thecontainer at its destination, the container may be opened and the tanksections may be removed and quickly assembled by following the procedureoutlined previously.

Referring now to Figs, 3 and e, the present invention contemplates theprovision of an auxiliary wing tip fuel tank of alternative construemtion, this tank also being of the multi-sectional knock-down type. Thetank 5G includes a nose section Si, an intermediate section 52 and atail section 53 having a detachable tip 5d. La the first described formof the invention shown in Figs. l and 2, the tail section of the tankhas an intermediate cylindrical portion of reduced diameter tofacilitate nesting of the parts in the dismantled tank assembly. in thissecond form of the invention shown in Figs. 3 and 4, the nose section ofthe tank is likewise formed with an intermediate cylindrical portion ofreduced diameter for the same purpose of facilitating nesting of theparts in the dismantled tank assembly.

rlhe nose section 5l is of conoidal shape and has a flanged ring 5t atits rearward open end, the ring having an annular socket or recess inwhich is disposed a compressible sealing ring 5l. Substantially midwaybetween its ends the nose section has an intermediate cylindricalportion 58 forming an annular recess or step. A fairing band or splitring 60 of frusto-conical shape is normally disposed in said recess orstep, being retained in place by screws iii which pass through aperturesin clamping strips E52 carried by the ends of the band.

The intermediate tank section 52 is cylindrical and has a flange elementE5 at one end provided with an annular bead G5 which engages against thesealing ring 5i of the nose section 5i to compress the ring so as toeffect a fluid-tight joint. At its rearward end, the intermediatesection 52 has a ange element Sl which carries a compressible sealingring $8.

The tail section 53 is of frusto-conical shape and has a ange element'iii at its forward, larger end portion, the element having an annularbead li which engages the ring 6B to compress the same so as to providea fluid-tight joint. Adjacent its larger, forward end portion, the tailsection 53 has an intermediate cylindrical portion '12 which is normallycovered by a fairing band 15. Screws i5 passing through holes inclamping strips 'Vi provided at the ends of the band i5 retain the bandin position overlying the cylindrical portion l2.

At its rearward, smaller end, the tail section 53 is reduced in diameterto receive the forward open end of the tail tip et, which is of conicalshape. An annular, hanged attaching element l5 is secured to therearward end of the tail section 553 and is provided with nuts Sii forreceiving screws Si `which pass through holes in the forward end of thetail tip at to retain the latter in place. A similar element 83 isfastened to the interior of the tail section 53, inwardly of the elementis and has a tubular central portion 2d providing a bearing forreceiving the cap Sii of the clamping means t6, the latter being similarto the clamping means d5, previously described.

In accordance with the present concept, the tank sections 5i to tip 54,and associated parts 69, l5, Sii, etc., are shipped to airiields inunassembled condition, the components being later assembled to producethe auxiliary fuel tanks as needed by the Air Force. As in thepreviously described tank 5, the various parts of the tank are adaptedto be packaged in nested relationship so as to conserve shipping andstorage space. Referring to Fig. 4, the fairing bands t6 and l5 arefirst placed in the intermediate tank section 52, the ends of the ringsbeing disconnected to allow contraction thereof so as to facilitatetheir insertion into the section 52. The smaller, rearward end of thetail section is then slid into the intermediate section 52 with itsintermediate cylindrical portion 'i2 sliding into the bead 65 thereof.The forward, pointed end of the nose section 5i is then slid into thetail section 53, it being noted that the diameter of the step portion 58of the tail section is made slightly smaller than the inside diameter ofthe bead "il to facilitate such nesting of the nose section Iwithin thetail section. The tail tip 5t, the parts of the clamping means 86, etc.,are then placed in the nose section 5l and the entire group of tankcomponents may be crated in their knocked-down, nested relation forshipment or storage. The group or package of nested tank elementsoccupies only a fraction of the space required for a completelyassembled fuel tank of the same shape and size as the tank 5c. Byproviding the nose and tail sections with the annular depressions orcylindrical portions 58 and l2, the various anonimi.

7. components may be: nested with considerably7 more compactness, ithaving been. determined that slightly more than 21/2 of the knocked-downpackages can be shipped: orrstoredf in. the; spacer the particular stepsbeing more. or: less.v selective.

or arbitrary. While the` knock-dovvnfuel tank has been hereindisclosed'. as embodied'` in two specific forms, it. is obvious thatthe. shape. andv size of the improved tank may be. Varied;in certainrespectswithin the. concept ofthis invention,

I claim as `my invention: 1. A smoothly streamlined auxiliary' wing-tipfuel tank of. knock-down construction. free. from externa-l peripheralprojections comprising a plurality of tank sections joinedltcgether withgirthV parting lines, said tank. sections having: girth reinforcementmembers. inside their peripheral walls positioned to lie on oppositesides. ofi each parting line, said reinforcement members being adaptedfor sealing cooperation.alcngrtheparting.

lines, said tank sections including an intermediate tank section andtwovend tank sections, each of said end tank sections being tapered at onevof its ends and being dimensioned atthev other end to match one end ofsaid intermediate' tank sec.- tion, at least one of said end tank.sections having an intermediate portion of reduced crosssecticndimensione'd to telescope into the girth reinforcement member atcneiend. of said intermediate tank section. Whereby the dismantled tanksections may be nested together with said one end tank sectionnested'ins yicl intermediateV tank section and the other end tanksection nested in said one end tank sectionA to form a compactdismantled tank assembly.

2. A combination as set forthV in claim 1; in which said tank sectionsare circular in. crosssection.

3. A combination as set forth in. claim 2 in which said intermediateVtank section is, a cylinder of uniform diameter.

4. A combination as set forth claim" l: in which one of said end tanksections has atip detachable therefrom forv stom/'age'v in. saiddismantled tank assembly.

A smoothly streamlined auxiliary Wing-tip fuel tank of knock-downconstruction freefrorn.

inforcement members insidev their peripheral. Walls positioned to lie onopposite sides' ofeach.

parting line, said reinforcement members being Cil adapted for sealingcooperation along the parting. lines, said tank sections including anintermediate tank section and two end tank sections, each of said endtankr sections being tapered at one of its ends and being dimensioned atthe other end to match one' end of said intermediate tank section, atleast one of said end tank sectionshavin'g an intermediate portion ofuniform cross-section merging at one end with the tapered portion. of`the` same end tank section and terminating at its other end in a girthshoulder stepping up thecross-sectional dimension of the same; end tanksection, said intermediate portion of the end tank section beingdimensioned to telescope into the girth reinforcement member at one endof said intermediate tank section Whereby: the dismantled tank sectionsvmay be nested together with said one end tank section nested in saidintermediate tank section and the other end tanksection nested in saidone end tank section to form a compact dismantled tank assein bly.

6. A combination as set forth in claim 5 which includes a removablefairing ring to embrace said uniform intermediate portion of said oneend tank section to provdefa smooth transition from the tapered portionof the tank section to the stepped up cross-sectionV of the same endtank section, said fairing ring being dimensioned for inclusion in saiddismantled tank assembly.

7. A combination asset forth in claim (iv in which said tank sectionsare circular in crosssection and said intermediate tank section is acylinder of uniformY diameter throughout its length.

8. A combination as set forth in claim 7 in which one of said end tanksections has a tip detachable therefrom for stoWage in said dismantledassembly.

9. A combination as set forth in claim 8 in which said one end tanksection has a detachable tip and an internal circular seat to receivesaid'tip in the dismantled tank assembly and for service in connectingsaid tank sections together to form a complete' tank.

WENDELL S. FLETCHER.

ci'erences Citedin thev fiie' of this patent UNITES STATES PATENTSNumber Name Date 888,943 Tuttle May 26, 1908 1,183,928 Webb May- 23,1916 1,376,216 Mittinger Apr. 26, 1921 1,595,633 'Ihwaits Aug. l0, 19262,300,259 Kueppers Oct. 27, 1942 2,471,296 Allen et al May 24, 19492,545,481 Maier Mar. 223, 195i

